Description of Related Art
Recently, according to the trend toward electric automobiles or hybridization of automobiles and multiplexing of electric signals for controlling electric and electronic devices mounted in automobiles, an electromagnetic shield technique is strongly desired for various kinds of electric wires and connectors comprising a wire harness to serve as a cable way.
In the case of the connectors, the shield effect with respect to electromagnetic waves is required for both preventing radiation of the electromagnetic waves from a terminal accommodated in a connector housing to the outside and preventing influence on an electric signal in a terminal in a connector housing from the outside electromagnetic waves.
In order to meet such demands, various proposals have been provided.
For example, Japanese Patent Publication No. 10-144406A discloses a method for providing a shield effect with conductive material powders by introducing powders of a conductive material having the excellent absorbing property with respect to electromagnetic waves, such as ferrite into the outer wall of a resin connector housing or a resin cover for covering the periphery of the connector housing.
Moreover, Japanese Patent Publication No. 8-298168A discloses a method for providing a desired shield effect with an electromagnetic blocking plate by providing an electromagnetic blocking plate comprising a metal plate in a resin connector housing or on the outer surface thereof.
Furthermore, a method for providing a desired shield effect with a conductive thin film by providing a conductive thin film on the outer surface of a resin connector housing by applying electroless plating or a conductive coating is proposed.
However, the method of introducing conductive material powders into a resin connector housing or cover arises a problem in that there is a risk of partially producing a portion having a low shield effect unless the conductive material powders are dispersed homogeneously and with an appropriate concentration in the resin material and thus it is difficult to obtain a stable shield performance. Moreover, since a step of mixing and agitating the conductive material powders in the resin material is required, problems of the material cost rise and the connector cost rise due to complication of the connector forming process are involved.
Further, the method of providing a shield effect with the electromagnetic blocking plate comprising a metal plate arises a problem in that the weight of the connector is increased due to the weight of the metal plate. Moreover, a problem of drastic cost rise of the connector due to increase of the number of components of the connector is involved.
Further, the method of providing the shield effect with the conductive thin film formed by application of electroless plating or a conductive coating arises a problem in that the film thickness of the formed conductive thin film tends to be irregular in the case the connector housing has a complicated structure with many projections and recesses so that there is a risk of partially producing a portion having a low shield effect due to the film thickness irregularity, and thus it is difficult to obtain a stable shield performance. Moreover, since the forming process of the conductive thin film is required as a formation step of the connector and the material cost of the conductive thin film is needed, a problem of cost rise is involved.